This invention pertains to a multiple displacement pump system and, more particularly, a system having a fixed displacement vane-type pump having a first set of pumping chambers between the vanes and a second set of pumping chambers beneath the vanes with circuit means to deliver fluid to a downstream fluid utilization conduit which may be either the sum of fluid delivered from both sets of pumping chambers or fluid from only one set of pumping chambers, with return of the non-utilized fluid to one of said sets of pumping chambers.
The prior art includes disclosures of pumps with pumping elements which have two sets of pumping chambers defined by spaces between the pumping elements and spaces beneath the pumping elements. This prior art includes Finlayson et al U.S. Pat. No. 2,511,573, Vickers U.S. Pat. No. 2,570,411, and Lock U.S. Pat. No. 3,639,089. These patents do not have any disclosure of either fluid inlet means or fluid outlet means with separate conduits providing for selective volumes of flow of fluid from the pump, dependent upon flow in one of the separate conduits being cross-connected to the other side of the fluid path whereby the cross-connected flow does not reach a fluid utilization conduit downstream of the control.
Additional prior art patents disclose pumps having first and second sets of pumping chambers, with separate conduits for flow from the respective sets of pumping chambers. This prior art includes Links U.S. Pat. No. 2,688,924, Poulin U.S. Pat. No. 3,043,234, and Bellmer U.S. Pat. No. 3,565,550. These prior art patents do not show circuit means associated with the fluid inlet and outlet means for the pump providing for suitable cross-connection therebetween whereby fluid may be delivered to a fluid utilization conduit and which is either the sum of fluid delivered from both sets of pumping chambers or from only one set of pumping chambers.
The prior art has also recognized the concept of taking two outlet flows from a pump, as shown in Adams et al U.S. Pat. No. 2,832,199 and Brundage U.S. Pat. No. 3,128,707; however, these two fluid outlet paths are not provided by outlets from two distinct sets of pumping chambers arranged between and beneath the pumping elements, respectively.